1. Field of the Invention
The present invention relates generally to inductively coupled plasma sources and plasma generation, and more particularly, to an inductively coupled plasma source and process of plasma generation capable of preventing etching of the interior of a reactor due to sputtering of plasma gas.
2. Description of Related Art
Plasma sources are widely used in several processes during the manufacture of semiconductor devices, such as etching, stripping and cleaning of the devices. In processes that use plasma, the density and uniformity of the plasma generation affect the efficiency of the process. Consequently, several efforts have been made to increase the density and uniformity of plasma generation, and various proposals have been made for more effectively obtaining plasma. A high frequency power source must be used to obtain the plasma however, and this creates several problems that have long plagued the art.
A plasma source may be classified roughly into capacitively coupled plasma and inductively coupled plasma according to the particular principle of plasma generation. A plasma source using the inductively coupled plasma is described in U.S. Pat. No. 4,431,898 entitled Inductively Coupled Discharge For Plasma Etching and Resist Stripping, granted to Alan R. Reinberg on the 14th day of February 1984 (hereinafter called Reinberg ""898). In this patent, Alan R. Reinberg proposes an inductively coupled plasma source that uses a plasma chamber having a toroidal tube structure to which an A.C. (alternating current) power source is supplied. The tube structure acts as both primary and secondary windings. A transformer core transmits the energy from the primary winding to the secondary winding.
Since the aforementioned plasma source proposed by Reinberg ""898 uses a transformer with complex turns, the efficiency of the energy transmission is very low. As a result, the efficiency of ionization is also low and the plasma is liable to be extinguished. A supply of high energy is necessary in order to stabilize generation of the plasma. In this case, a high frequency power source, which is very expensive, must be used. Consequently, a high initial cost as an investment in the facility is required. Moreover, the inner wall of the plasma chamber with a toroidal tube structure is etched by the collision of the ions in the plasma. I have discovered that there is a need for some solution to prevent etching of the plasma reactor.
The present invention is disclosed in order to overcome the aforesaid drawbacks of the prior art.
It is therefore, one object of the present invention to provide an improved plasma generating process and source.
It is another object to provide an inductively coupled plasma source capable of increasing efficiency of generation of the plasma.
It is yet another object to provide a more efficient plasma generating process and inductively coupled source.
It is still another object to provide a plasma generating process and inductively coupled source that minimizes the etching of the plasma reactor.
It is still yet another object of the present invention to provide a plasma generating process and an inductively coupled plasma source capable of preventing etching of the inner wall of the plasma reactor due to collisions of the ions in plasma form.
According to one aspect of the present invention, to accomplish the objects of the invention as mentioned above, a plasma generating process and an inductively coupled plasma source may be constructed with a reactor including a gas inlet, a gas outlet, and a tube structure that has a conductive layer with a open loop. The tube structure is disposed between two non-conductive layers having a continuous loop providing a discharge path. An A.C. power source supplies A.C. voltage to the conductive layer. A magnetic field is induced by the flow of alternating current through the conductive layer to which the A.C. voltage is supplied, and a secondary electric field is generated through the discharge path by the inducted magnetic field, which, in turn, causes the occurrence of plasma discharge.
In the practice of the present invention, the inductively coupled plasma source may use at least one transformer core disposed in the tube structure to reinforce the inducted magnetic field.
In an alternative embodiment of the present invention, the inductively coupled plasma source may be constructed with a D.C. power source for supplying D.C. voltage to the conductive layer, and an inductor electrically may be connected between the conductive layer and the D.C. power source. A condenser may be electrically connected between the conductive layer and the A.C. power source, so that the conductive layer is coupled to the A.C. power source, and is thus supplied with a positive voltage biased by means of the D.C. voltage applied by the D.C. voltage.
In the practice of the present invention, the conductive layer may be tubular or coil-shaped.
Various modifications and changes of the present invention may be made to these embodiments in accordance with the principles of the invention, and it is to be distinctly understood that the scope of invention is not limited to the embodiments as mentioned below. It should be noted that the embodiments of the present invention are provided to explain the invention more clearly to those who have ordinary skill in the art. Therefore, shape or the like of the elements in the drawings is exaggerated for the purpose of more clear and accurate explanation.